Distance measurement using EHF signals

Abstract

A system for sensing proximity using EHF signals may include a communication circuit configured to transmit via a transducer an EM signal at an EHF frequency, and a proximity sensing circuit configured to sense a nearby transducer field-modifying object by detecting characteristics of a signal within the communication circuit. A system for determining distance using EHF signals may include a detecting circuit coupled to a transmitting communication circuit and a receiving communication circuit, both communication circuits being mounted on a first surface. The transmitting communication circuit may transmit a signal toward a second surface, and the receiving communication circuit may receive a signal relayed from the second surface. The detecting circuit may determine distance between the first surface and a second surface based on propagation characteristics of the signals.

We claim: 
     
       1. A system comprising:
 a first transmit communication unit mounted on a first surface for transmitting a receive EHF signal toward a second surface spaced from the first surface; 
 a first receive communication unit mounted on the first surface adjacent the first transmit communication unit for receiving a receive EHF signal transmitted from the second surface; 
 a detecting circuit coupled to the first transmit communication unit and the first receive communication unit for determining an indicator representative of a distance between the first and second surfaces based on the propagation of the transmit and receive EHF signals between the first transmit communication unit and the first receive communication unit; 
 wherein a second transmit communication unit and a second receive communication unit mounted on the second surface; wherein the first transmit communication unit transmits the transmit EHF signal to the second receive communication unit, the second receive communication unit is coupled to the second transmit communication unit and communicates a communication signal representative of the transmit EHF signal received by the second receive communication unit to the second transmit communication unit, and the second transmit communication unit transmits to the first receive communication unit the receive EHF signal representative of the communication signal; and 
 wherein the first receive communication unit is coupled to the first transmit communication unit, with the first and second transmit communication units and first and second receive communication units forming in combination a ring oscillator. 
 
     
     
       2. The system of  claim 1 , wherein the detecting circuit determines an oscillation period of the ring oscillator, the oscillation period being related to a distance between the first surface and the second surface. 
     
     
       3. A method comprising:
 transmitting by a first transmit communication unit mounted on a first surface, a transmit EHF signal toward a second surface; 
 receiving, by a first receive communication unit mounted on the first surface adjacent the first transmit communication unit, a receive EHF signal transmitted from the second surface; 
 generating, by a detecting circuit coupled to the first transmit communication unit and the first receive communication unit, an indicator representative of a distance between the first and second surfaces based on the propagation of the transmit and receive EHF signals between the first transmit communication unit and the first receive communication unit; 
 transmitting the transmit EHF signal to a second receive communication unit mounted on the second surface; communicating a communication signal representative of the transmit EHF signal received by the second receive communication unit to a second transmit communication unit mounted on the second surface, and transmitting by the second transmit communication unit the receive EHF signal representative of the communication signal to the first receive communication unit; 
 further comprising coupling the first receive communication unit to the first transmit communication unit so that the first and second transmit communication units and the first and second receive communication units form in combination a ring oscillator. 
 
     
     
       4. The method of  claim 3 , wherein generating an indicator includes determining an oscillation period of the ring oscillator, the oscillation period being related to a distance between the first surface and the second surface.